The photo below shows the helix base pulled away from the layout to provide all round access to build the helix and lay the track
The two pieces that make up the helix road bed being laminated together, the track on the right leads from the top down to the lower deck and had to have enough clearance for tall rolling stock. The left side track is from the lower level up to the top deck.
Once the first loop was finished I decided to start installing the supports for the rest of the decks, you can see the flat car with the tank on it to test the clearances because it is the widest piece of rolling stock I have.
To save a bit of time and difficulty I paint the sections first before gluing them together, the construction usually goes in this order.
Paint some sections, then lay track on the last completed section on the helix then glue the next section.
Like a nong I was hooking up a controller up to the track to test the alignment and joints with a loco, I saw a bloke on youtube testing his track with a 9V battery to run the loco, goes to show you learn something every day.
The time and effort to get the base right was worth it because all I have to do is place some spacer blocks to get the correct height for the next level.